Global warming natural cycle: understanding the difference between the main climate drivers of the natural Milankovitch Cycles and how that influences natural variation in ice, oceans, vegetation and seasons, helps us understand how the earth moves in and out of ice ages. From this context we can more easily understand the forces involved in our current global warming. Written & narrated by John P. Reisman. Science review by: Mike (Michael) Mann, Jeff Severinghaus, and James Maslanik, with special thanks to Ralph Keeling, David Archer, and Bette L. Otto-Bliesner.